#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
int main()
{
    double r1 = 0;
    double r2 = 0;
    scanf("%lf%lf", &r1, &r2);
    double r3 = (r1 * r2) / (r1 + r2);
    printf("%.1f\n", r3);

    return 0;
}